JP2012187390A - Photoacoustic image generation apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a photoacoustic image generation apparatus which can use two laser operation modes by switching them.SOLUTION: A trigger control circuit 24 outputs a laser trigger signal to a laser unit 13. A trigger controller 31 outputs a Q-SW trigger signal at an indefinite time relative to the trigger signal in a first operation mode, and also outputs a synchronization signal. In a second operation mode, a Q-SW trigger signal is output at a fixed time relative to the trigger signal. A/D conversion means 22 samples a photoacoustic signal detected by a probe 11. A sampling control circuit 25 initiates a sampling in the A/D conversion means 22 in synchronization with the synchronization signal in the first operation mode. In the second operation mode, the sampling in the A/D conversion means 22 is initiated in synchronization with the laser trigger signal.

Description

  The present invention relates to a photoacoustic image generation apparatus, and more particularly to a photoacoustic image generation apparatus that irradiates a subject with laser light and detects ultrasonic waves generated in the subject due to laser light irradiation.

  An ultrasonic inspection method is known as a kind of image inspection method capable of non-invasively examining the state inside a living body. In the ultrasonic inspection, an ultrasonic probe capable of transmitting and receiving ultrasonic waves is used. When ultrasonic waves are transmitted from the ultrasonic probe to the subject (living body), the ultrasonic waves travel inside the living body and are reflected at the tissue interface. By receiving the reflected sound wave with the ultrasonic probe and calculating the distance based on the time until the reflected ultrasonic wave returns to the ultrasonic probe, the internal state can be imaged.

  In addition, photoacoustic imaging is known in which the inside of a living body is imaged using a photoacoustic effect. In general, in photoacoustic imaging, a living body is irradiated with pulsed laser light. Inside the living body, the living tissue absorbs the energy of the pulsed laser light, and ultrasonic waves (photoacoustic signals) are generated by adiabatic expansion due to the energy. By detecting this photoacoustic signal with an ultrasonic probe or the like and constructing a photoacoustic image based on the detection signal, in-vivo visualization based on the photoacoustic signal is possible.

  Here, a biological information measuring device based on photoacoustics is described in Patent Document 1. The biological information measuring device described in Patent Literature 1 includes a light source, a control unit that controls the light amount and lighting timing of the light source, a biological information sensor that measures biological information, and a biological information based on a signal detected by the sensor. Feature amount estimating means for estimating the feature amount. In the biological information measuring apparatus, when the patient starts measurement, the amplification means, the A / D conversion means, etc. are activated, and the lighting timing and light quantity of the light source are controlled at the same timing when they enter stable operation, and the light source is turned on. To do.

JP 2009-39268 A

  In Patent Document 1, there is no description as to when light is actually irradiated with respect to the control signal when the control means controls the lighting timing of the light source. If light irradiation is performed at a certain timing with respect to the control signal, the light amount of the emitted laser light is not necessarily optimized although the timing is easily controlled. Conversely, when the amount of emitted laser light is optimized, the laser emission timing becomes indefinite with respect to the control signal. Conventionally, these two laser emission timings (laser operation modes) have not been switched and used.

  In view of the above, an object of the present invention is to provide a photoacoustic image generation apparatus that can be used by switching between two laser operation modes.

  In order to achieve the above object, the present invention operates in a trigger control circuit that outputs a trigger signal for instructing light emission, a first operation mode, and a second operation mode. A light source unit that emits light at an indefinite timing with respect to the trigger signal and outputs a synchronization signal indicating the light emission timing; and in the second operation mode, emits light at a constant timing with respect to the trigger signal; A signal detecting means for detecting a photoacoustic signal generated in the subject after the light emitted from the light source unit is irradiated on the subject; a sampling means for sampling the detected photoacoustic signal; and the sampling When the photoacoustic image generation means for generating a tomographic image based on the photoacoustic signal thus generated and the light source unit operate in the first operation mode, the synchronization signal In this case, sampling of the photoacoustic signal in the sampling unit is started. When the light source unit operates in the second operation mode, sampling for starting the sampling of the photoacoustic signal in the sampling unit in synchronization with the trigger signal is performed. There is provided a photoacoustic image generation device comprising a control circuit.

  In the present invention, the light source unit includes a trigger controller and a Q-switched laser. When the trigger controller receives a trigger signal output from the trigger control circuit, the excitation of the Q-switched laser is started, In the operation mode, it is possible to employ a configuration in which the Q switch is controlled at an indefinite timing after the excitation is started, and in the second operation mode, the Q switch is controlled at a certain timing from the start of the excitation.

  In the first operation mode, the trigger controller may output a signal indicating the timing for controlling the Q switch as a synchronization signal.

  The light source unit may monitor the amount of emitted light at the time of light emission, and may determine the light emission timing based on the amount of light monitored at the time of the previous light emission in the first operation mode.

  The photoacoustic image generation apparatus of the present invention may employ a configuration further comprising mode switching means for switching the operation mode of the light source unit between the first operation mode and the second operation mode. .

  In the present invention, when generating photoacoustic volume data indicating photoacoustic three-dimensional information, the mode switching unit may set the operation mode of the light source unit to the second operation mode.

  In the generation of the photoacoustic volume data, the signal detection unit may be scanned, and the sampling unit may sample the photoacoustic signals detected at a plurality of scanning positions.

  The photoacoustic image generation apparatus of the present invention may further include a projection image generation unit that generates a photoacoustic projection image obtained by projecting the photoacoustic signal generation source in the depth direction at each of the plurality of scanning positions. Good.

  The projection image generation means may generate a portion corresponding to the scanning position of the photoacoustic projection image based on the photoacoustic signal detected at each scanning position before the scanning is completed. Good.

  The projection image generation means integrates the absolute value of the detected photoacoustic signal in the depth direction, and a portion corresponding to the scanning position of the photoacoustic projection image based on the integrated photoacoustic signal. Can be generated.

  The projection image generation unit may generate the photoacoustic projection image in parallel with the scanning of the signal detection unit.

  At each of the plurality of scanning positions, a reflected ultrasonic signal for the ultrasonic wave transmitted to the subject is detected, and in addition to the photoacoustic volume data, ultrasonic volume data indicating three-dimensional information of the reflected ultrasonic wave is generated. You may do here.

  The projection image generation unit generates an ultrasonic projection image obtained by projecting the reflected ultrasonic signal in the depth direction at each of the plurality of scanning positions instead of or in addition to the acoustic projection image. Also good.

  The photoacoustic image generation apparatus of the present invention may further include a scanning mechanism that scans the signal detection unit in a predetermined scanning direction.

  The scanning mechanism may include a holding unit that holds the signal detection unit and a moving unit that moves the holding unit in a predetermined scanning direction.

  The present invention also includes a step of outputting a trigger signal for instructing light emission to a light source unit operable in either the first operation mode or the second operation mode, and the light source unit includes: In the first operation mode, light is emitted at an indefinite timing with respect to the trigger signal and a synchronization signal indicating the light emission is output, and in the second operation mode, light is emitted at a constant timing with respect to the trigger signal. Detecting a photoacoustic signal generated in the subject after the light emitted from the light source unit is irradiated on the subject, and when the light source unit operates in the first operation mode, The sampling of the photoacoustic signal is started in synchronization with the synchronization signal, and when the light source unit operates in the second operation mode, the sample of the photoacoustic signal is synchronized with the trigger signal. And initiating a ring, to provide a photoacoustic image generation method and a step of generating a photoacoustic tomographic image on the basis of the sampled photoacoustic signals.

  The photoacoustic image generation apparatus of the present invention includes a first operation mode in which light is emitted at an indefinite timing with respect to a trigger signal, and a second operation mode in which light is emitted at a constant timing with respect to the trigger signal. Can be switched. For example, by optimizing the laser emission timing in the first operation mode, the amount of light irradiated to the subject can be maximized. As a result, the signal level of the photoacoustic signal can be prevented from being lowered, and a good photoacoustic image can be generated. On the other hand, in the second operation mode, the subject can be irradiated with light at a certain timing, so that image generation with priority given to timing can be performed.

The block diagram which shows the photoacoustic image generating apparatus of 1st Embodiment of this invention. The flowchart which shows the operation | movement procedure in laser master mode. The flowchart which shows the operation | movement procedure in ultrasonic master mode. The block diagram which shows the photoacoustic image generating apparatus of 2nd Embodiment of this invention. The figure which shows the structural example of a probe scanning mechanism. The block diagram which shows a projection image generation part and a tomographic image generation part.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 shows a photoacoustic image generation apparatus according to a first embodiment of the present invention. The photoacoustic image generation apparatus (photoacoustic image diagnostic apparatus) 10 includes an ultrasonic probe (probe) 11, an ultrasonic unit 12, and a laser light source (laser unit) 13. The photoacoustic image diagnostic apparatus 10 can generate both an ultrasonic image and a photoacoustic image. The laser unit (light source unit) 13 generates laser light to be irradiated to a subject when generating a photoacoustic image. What is necessary is just to set the wavelength of a laser beam suitably according to an observation target object. The laser light emitted from the laser unit 13 is guided to the probe 11 using light guide means such as an optical fiber, and is irradiated from the probe 11 to the subject.

  The probe 11 is signal detection means, and outputs (transmits) ultrasonic waves to the subject and detects (receives) ultrasonic waves from the subject. The probe 11 has, for example, a plurality of ultrasonic transducers arranged one-dimensionally. The probe 11 outputs ultrasonic waves from a plurality of ultrasonic transducers when generating an ultrasonic image, and detects reflected ultrasonic waves (hereinafter also referred to as reflected acoustic signals) with respect to the output ultrasonic waves. When the photoacoustic image is generated, the probe 11 detects an ultrasonic wave (hereinafter also referred to as a photoacoustic signal) generated when the measurement target in the subject absorbs the laser light from the laser unit 13.

  The ultrasonic unit 12 includes a reception circuit 21, an AD conversion unit 22, an image generation unit 23, a trigger control circuit 24, a sampling control circuit 25, a control unit 26, a transmission control circuit 27, and a mode switching circuit 28. The receiving circuit 21 receives ultrasonic waves (photoacoustic signals or reflected acoustic signals) detected by a plurality of ultrasonic transducers included in the probe 11. The AD conversion means 22 is a sampling means, and converts the ultrasonic signal received by the receiving circuit 21 into a digital signal. The AD conversion means 22 samples an ultrasonic signal with a predetermined sampling period in synchronization with, for example, an AD clock signal input from the outside.

  The image generation means (tomographic image generation means) 23 generates a tomographic image based on the ultrasonic waves sampled by the AD conversion means 22. The image generation unit 23 generates a photoacoustic image based on the photoacoustic signal detected by the probe 11 and generates an ultrasonic image based on the reflected acoustic signal detected by the probe 11. The image generation unit 23 includes an image reconstruction unit 231, a detection unit 232, a logarithmic conversion unit 233, and an image construction unit 234. The function of each part in the image generation means 23 can be realized by the computer operating the process according to a predetermined program. In FIG. 1, the photoacoustic image and the ultrasonic image are generated by the same image generation unit 23, but the photoacoustic image and the ultrasonic image are separated into separate image generation units (photoacoustic image generation unit and ultrasonic wave). It may be generated by image generation means).

  The image reconstruction unit 231 generates data for each line of the tomographic image based on the ultrasonic signals detected by the plurality of ultrasonic transducers of the probe 11. For example, the image reconstruction unit 231 adds data from 64 ultrasonic transducers of the probe 11 with a delay time corresponding to the position of the ultrasonic transducer to generate data for one line (delay addition method). ). The image reconstruction unit 231 may perform reconstruction by the CBP method (Circular Back Projection) instead of the delay addition method. Alternatively, the image reconstruction unit 231 may perform reconstruction using a Hough transform method or a Fourier transform method.

  The detection unit 232 outputs an envelope of the data of each line output by the image reconstruction unit 231. The logarithmic conversion means 233 performs logarithmic conversion on the envelope output from the detection means 232 to widen the dynamic range. The image construction unit 234 generates a tomographic image based on the data of each line subjected to logarithmic transformation. The image construction unit 234 generates a tomographic image by converting, for example, a position in the time axis direction of the ultrasonic signal (peak portion) into a position in the depth direction in the tomographic image. The image display unit 14 displays the tomographic image generated by the image construction unit 234 on a display monitor or the like.

  The control means 26 controls each part in the ultrasonic unit 12. The control means 26 notifies the trigger control circuit 24 of the start of generation of the ultrasonic image or photoacoustic image. When generating an ultrasonic image, the trigger control circuit 24 sends an ultrasonic transmission trigger signal to the transmission control circuit 27 to instruct ultrasonic transmission. When receiving the trigger signal, the transmission control circuit 27 transmits an ultrasonic wave from the probe 11. The ultrasonic transmission does not necessarily have to be performed from the probe 11, and the ultrasonic transmission may be performed from a place other than the probe 11. On the other hand, the trigger control circuit 24 sends a laser trigger signal for instructing the laser unit 13 to emit light when generating the photoacoustic image. The laser unit 13 emits laser light after receiving the laser trigger signal.

  Here, the laser unit 13 operates in two operation modes: a laser master mode (first operation mode) and an ultrasonic master mode (second operation mode). In the laser master mode, the laser unit 13 emits light at an indefinite timing with respect to the laser trigger signal from the ultrasonic unit 12. In addition, a synchronization signal indicating the light emission timing is output to the ultrasonic unit 12. In the ultrasonic master mode, the laser unit 13 emits light at a certain timing with respect to the laser trigger signal from the ultrasonic unit 12.

  The sampling control circuit 25 outputs an AD trigger signal to the AD conversion means 22 and controls the sampling start timing in the AD conversion means 22. When the AD conversion means 22 receives the AD trigger signal, it starts sampling. The sampling control circuit 25 sends an AD trigger signal to the AD conversion means 22 at a predetermined timing that has a fixed time relationship with the output timing of the ultrasonic transmission trigger signal when the ultrasonic image is generated. In other words, the sampling control circuit 25 starts sampling of the reflected acoustic signal in the AD conversion means 22 in synchronization with the ultrasonic transmission trigger signal.

  When generating the photoacoustic image, if the operation mode of the laser unit 13 is the laser master mode, the sampling control circuit 25 performs AD at a predetermined timing that has a fixed time relationship with the timing at which the synchronization signal is received from the laser unit 13. An AD trigger signal is sent to the conversion means 22. In other words, the sampling control circuit 25 starts sampling of the photoacoustic signal in the AD conversion unit 22 in synchronization with reception of the synchronization signal. If the operation mode of the laser unit 13 is the ultrasonic master mode, the sampling control circuit 25 sends an AD trigger signal to the AD conversion means 22 at a predetermined timing that has a fixed time relationship with the output timing of the laser trigger signal. In other words, the sampling control circuit 25 starts sampling of the photoacoustic signal in the AD conversion means 22 in synchronization with the laser trigger signal.

  The mode switching circuit (mode switching means) 28 switches the operation mode (laser operation mode) of the laser unit 13 between the laser master mode and the ultrasonic master mode. The mode switching circuit 28 switches the operation mode of the laser unit 13 based on, for example, an instruction from the user. The user can arbitrarily select an operation mode according to his / her preference and the purpose of image generation. The mode switching circuit 28 may automatically switch the operation mode of the laser unit 13 based on, for example, the photoacoustic image generation conditions and purpose. For example, the mode switching circuit 28 can be set to the laser master mode when observing a tomographic image, and can be set to the ultrasonic master mode when acquiring volume data.

  The laser unit 13 includes a trigger controller 31 and a Q switch laser 32. The Q-switched laser 32 includes a flash lamp 321 that is an excitation light source and a Q-switch 322 that controls laser oscillation. When the laser trigger signal from the ultrasonic unit 12 is input, the trigger controller 31 turns on the flash lamp 321 and starts excitation of a laser medium (not shown). If the operation mode is the laser master mode, the trigger controller 31 outputs a Q-SW trigger signal for turning on the Q switch 322 at an indefinite timing after the excitation is started, and emits a laser beam from the Q switch laser 32. Let it emit. If the operation mode is the ultrasonic master mode, the trigger controller 31 outputs a Q-SW trigger signal at a certain timing after the excitation is started, and causes the Q switch laser 32 to emit laser light.

  In the laser master mode, the trigger controller 31 optimizes the laser emission timing, for example, and controls the Q switch 322 at a timing at which a high laser output is obtained. For example, the trigger controller 31 monitors the amount of emitted light at the time of light emission, and determines the control timing of the Q switch with respect to the laser trigger signal so that a higher laser output can be obtained based on the amount of light monitored at the previous light emission. To do. In the laser master mode, by optimizing the laser emission timing, the time from when the laser unit 13 receives the laser trigger signal to when the laser emission is performed becomes indefinite. On the other hand, in the ultrasonic master unit, since the trigger controller 31 controls the Q switch 322 when a certain time has elapsed from the laser trigger signal, the period from when the laser unit 13 receives the laser trigger signal to when laser emission is performed. This time is a fixed time.

  In the laser master mode, the trigger controller 31 outputs a signal indicating the timing for controlling the Q switch 322 as a synchronization signal. The ultrasonic unit 12 can know at what timing light is emitted from the laser unit 13 based on the synchronization signal output from the laser unit 13. The sampling control circuit 25 starts sampling in the AD conversion means 22 in accordance with the light emission timing determined from the output timing of the synchronization signal. On the other hand, in the ultrasonic master mode, since the light emission timing is constant, no synchronization signal is required, and the sampling control circuit 25 adjusts the AD conversion means 22 in accordance with the light emission timing determined from the output timing of the laser trigger signal. Start sampling at.

  FIG. 2 shows an operation procedure when the laser operation mode is the laser master mode. The trigger control circuit 24 transmits a laser trigger signal to the laser unit (step A1). The trigger controller 31 of the laser unit 13 turns on the flash lamp 321 of the Q switch laser 32 and starts excitation of the laser medium (step A2). The trigger controller 31 outputs a Q-SW trigger signal to the Q switch 322 at a timing that is indefinite with the reception timing of the laser trigger signal (step A3). The Q switch 322 is turned on when a Q-SW trigger signal is input, the Q switch laser 32 oscillates, and the subject is irradiated with pulsed laser light. The trigger controller 31 outputs a synchronization signal to the ultrasonic unit 12 in accordance with the timing when the Q switch 322 is turned on (step A4).

  In the subject, a photoacoustic signal is generated by the irradiated pulsed laser beam. The probe 11 detects a photoacoustic signal generated in the subject (step A5). The sampling control circuit 25 outputs an AD trigger signal to the AD conversion means 22 in synchronization with the synchronization signal (step A6). When the AD trigger signal is input, the AD conversion means 22 samples the photoacoustic signal input via the receiving circuit 21 in synchronization with the AD clock signal input from the outside. The image generation means 23 generates a photoacoustic image based on the sampled photoacoustic signal (step A7). The image display unit 14 displays the generated photoacoustic image on the display screen (step A8).

  FIG. 3 shows an operation procedure when the laser operation mode is the ultrasonic master mode. The trigger control circuit 24 transmits a laser trigger signal to the laser unit (step B1). The trigger controller 31 of the laser unit 13 turns on the flash lamp 321 of the Q switch laser 32 and starts excitation of the laser medium (step B2). The trigger controller 31 outputs a Q-SW trigger signal to the Q switch 322 at a timing that has a certain relationship with the reception timing of the laser trigger signal (step B3). The Q switch 322 is turned on when a Q-SW trigger signal is input, the Q switch laser 32 oscillates, and the subject is irradiated with pulsed laser light.

  In the subject, a photoacoustic signal is generated by the irradiated pulsed laser beam. The wave probe 11 detects a photoacoustic signal generated in the subject (step B4). The sampling control circuit 25 outputs an AD trigger signal to the AD conversion means 22 in synchronization with the laser trigger signal (step B5). When the AD trigger signal is input, the AD conversion means 22 samples the photoacoustic signal input via the receiving circuit 21 in synchronization with the AD clock signal input from the outside. The image generation means 23 generates a photoacoustic image based on the sampled photoacoustic signal (step B6). The image display means 14 displays the generated photoacoustic image on the display screen (step B7).

  In the laser master mode, the amount of light applied to the subject can be increased by optimizing the laser emission timing. By maximizing the light applied to the subject, the image quality of the generated photoacoustic image can be improved. However, considering that the photoacoustic image is repeatedly generated, since the time from the output timing of the laser trigger signal to the laser unit 13 until the laser actually emits light is not constant, the photoacoustic image is displayed as a moving image. In this case, the frame rate varies.

  On the other hand, in the ultrasonic master mode, the laser emission timing is constant, so the laser does not necessarily emit light under optimum conditions, and the amount of light irradiated to the subject may be slightly reduced compared to the laser master mode. is there. For this reason, the signal level of the detected photoacoustic signal is slightly lowered as compared with the laser master mode. However, since the laser emission timing is constant, for example, when displaying a photoacoustic image as a moving image, the frame rate can be fixed at a constant rate. Further, since the ultrasonic unit 12 can predict when the laser beam is emitted, a synchronization signal is also unnecessary.

  For example, when the user wants to prioritize the image quality of the photoacoustic image, the user sets the laser operation mode to the laser master mode. In this case, the laser unit 13 can emit laser light under optimized conditions, and can prevent a decrease in the signal level of the photoacoustic signal. As a result, a high-quality photoacoustic image can be generated in the ultrasonic unit 12. For example, when the user wants to give priority to timing, the user sets the laser operation mode to the ultrasonic master mode. In this case, the laser irradiation timing from the laser unit 13 to the subject can be kept constant, and a photoacoustic image can be generated at a constant cycle. As a result, when displaying a photoacoustic image as a moving image, the photoacoustic image can be displayed at a constant frame rate. In this embodiment, the user uses the laser master mode in which the image quality of the photoacoustic image is high but the frame rate is not fixed, and the ultrasonic master mode in which the frame rate can be fixed but the image quality of the photoacoustic signal is slightly reduced. be able to.

  In the above embodiment, it has been described that the probe 11 transmits and receives ultrasonic waves and the image generation unit 23 can generate both a photoacoustic image and an ultrasonic image, but generation of an ultrasonic image is omitted. May be. In addition, when generating a photoacoustic image, it is also possible to generate an ultrasonic image at the same position and display the photoacoustic image and the ultrasonic image in an overlapping manner. In that case, it is preferable to superimpose the images so that the corresponding points of both images are in the same position.

  Then, the photoacoustic image generating apparatus of 2nd Embodiment of this invention is demonstrated. FIG. 4 shows a photoacoustic image generation apparatus according to the second embodiment of the present invention. In this embodiment, the probe 11 is scanned to acquire volume data. The probe 11 has, for example, a plurality of ultrasonic transducers arranged one-dimensionally, and the probe 11 is substantially orthogonal to the arrangement direction of the plurality of ultrasonic transducers arranged one-dimensionally. Volume data can be acquired by scanning in the direction. The scanning of the probe 11 is not limited to mechanical scanning, and may be electronic scanning. For example, when the probe 11 has a plurality of ultrasonic transducers arranged two-dimensionally, volume data may be acquired by electronically scanning the ultrasonic transducers arranged two-dimensionally.

  For the scanning of the probe 11, for example, a probe scanning mechanism 15 that automatically scans the probe 11 in a predetermined scanning direction is used. While the probe 11 is automatically scanned, pulsed laser light irradiation and photoacoustic signal detection are performed at a plurality of positions, and the photoacoustic signals detected at each position are combined to obtain photoacoustic volume data. . In addition, while automatically scanning the probe 11, ultrasonic waves are transmitted and reflected acoustic signals are detected at a plurality of positions, and the reflected acoustic signals detected at the respective positions are combined, so that the volume data of the reflected ultrasound is obtained. can get.

  FIG. 5 shows an example of the probe scanning mechanism 15. The probe scanning mechanism 15 includes a holding plate 81, a ball screw 82, a guide rod 83, and a motor 84. For example, the ball screw 82 and the guide rod 83 are vertically attached to the holding plate 81 so as to be parallel to each other. The ball screw 82 has a convex portion formed in a spiral shape. The motor 84 rotates the ball screw 82 in one direction and the opposite direction. The probe 11 is provided with a hole 80 through which the ball screw 82 passes and another hole through which the guide rod 83 passes.

  Here, the ball screw 82 and the guide rod 83 constitute a holding portion that holds the probe 11. The motor 84 that rotates the ball screw 82 constitutes a moving unit that moves the probe 11 in a predetermined scanning direction. The hole 80 through which the ball screw 82 passes is provided with a spiral recess (groove) corresponding to the spiral protrusion of the ball screw 82, and the probe 11 is rotated along with the rotation of the ball screw 82. It can move along the guide rod 83 in the W direction shown in FIG. By using such a probe scanning mechanism 15, the probe 11 can be precisely scanned.

  Returning to FIG. 4, the ultrasound unit 12 a in this embodiment includes a reception memory 41, a data separation unit 42, and an image synthesis unit 45 in addition to the configuration of the ultrasound unit 12 in the first embodiment shown in FIG. 1. . Further, in place of the image generation unit 23, a photoacoustic image reconstruction unit 43, an ultrasonic image reconstruction unit 44, a projection image generation unit 60, and a tomographic image generation unit 70 are provided. The photoacoustic image reconstruction unit 43, the ultrasonic image reconstruction unit 44, and the tomographic image generation unit 70 correspond to the image generation unit 23 of FIG. The photoacoustic image reconstruction unit 43 and the ultrasonic image reconstruction unit 44 correspond to the image reconstruction unit 231 of the image generation unit 23.

  The receiving circuit 21 receives an ultrasonic signal (a photoacoustic signal and a reflected acoustic signal) detected by the probe 11. The AD conversion reception circuit 21 samples the ultrasonic signal received by the reception circuit 21 and stores the sampling data in the reception memory 41. As the reception memory 41, any storage device such as a semiconductor storage device or a magnetic storage device can be used. The data separation unit 42 separates the acoustic wave detection signal and the ultrasonic wave detection signal stored in the reception memory 41. The data separation unit 42 inputs the separated acoustic wave detection signal to the photoacoustic image reconstruction unit 43 and inputs the ultrasonic detection signal to the ultrasound image reconstruction unit 44.

  The photoacoustic image reconstruction means 43 reconstructs a photoacoustic signal. The photoacoustic image reconstruction unit 43 outputs the reconstructed photoacoustic signal (reconstructed image) to the projection image generation unit 60 and the tomographic image generation unit 70. The ultrasonic image reconstruction unit 44 reconstructs the reflected acoustic signal. The ultrasonic image reconstruction unit 44 outputs the reconstructed reflected acoustic signal (reconstructed image) to the tomographic image generation unit 70.

  The projection image generation unit 60 generates a projection image (photoacoustic projection image) obtained by projecting the photoacoustic signal generation source in the depth direction at each of the plurality of scanning positions of the probe 11. The projection image generation unit 60 generates a projection image of a portion from the start of scanning to the current scanning position in parallel with the generation of volume data, for example. The projection image generation unit 60 outputs the generated projection image to the image synthesis unit 45.

  The tomographic image generation unit 70 generates a tomographic image at each scanning position of the probe 11. The tomographic image generation unit 70 generates a tomographic image at the current scanning position in parallel with the generation of volume data, for example. The tomographic image generation unit 70 generates a photoacoustic image (photoacoustic tomographic image) based on the photoacoustic signal, and generates an ultrasonic image (ultrasonic tomographic image) based on the reflected acoustic signal. The tomographic image generation unit 70 combines, for example, the generated photoacoustic tomographic image and ultrasonic tomographic image into one image and outputs it to the image combining unit 45.

  The image synthesizing unit 45 arranges the projected image and the tomographic image side by side on, for example, one display screen. For example, two images are arranged so that a tomographic image is displayed on the right side of the display screen and a projection image is displayed on the left side of the display screen. The image display unit 14 displays an image generated by the image synthesis unit 45 in which the projection image and the tomographic image are arranged on one display screen. After acquiring the volume data, a three-dimensional photoacoustic image may be generated based on the acquired volume data, and the three-dimensional photoacoustic image may be displayed on the display surface of the image display means 14.

  Here, instead of using the combined photoacoustic signal detected at each scanning position as the photoacoustic volume data, the combined photoacoustic signal reconstructed at each scanning position is used as the photoacoustic volume data. Also good. Alternatively, a photoacoustic tomographic image corresponding to each scanning position may be combined as photoacoustic volume data. Similarly, for reflected ultrasound, a combination of reconstructed reflected acoustic signals at each scanning position may be used as reflected ultrasound volume data, or an ultrasonic tomographic image corresponding to each scanning position is combined. May be reflected ultrasonic volume data.

  FIG. 6 shows details of the projection image generation unit 60 and the tomographic image generation unit 70. First, the projection image generation unit 60 will be described. The projection image generation unit 60 includes absolute value conversion means 61, depth direction data integration means 62, logarithmic conversion means 63, and projection image construction means 64. The absolute value converting means 61 obtains the absolute value of the reconstructed photoacoustic signal. The depth direction data integration means 62 integrates the photoacoustic signal converted into an absolute value in the depth direction (time axis direction). The logarithmic conversion means 63 logarithmically converts the photoacoustic signal integrated in the depth direction. This logarithmic conversion may be the same processing as the logarithmic conversion in the logarithmic conversion means 233 shown in FIG. The projection image construction means 64 images the photoacoustic signal generation source (light absorber) based on the logarithmically transformed integration value. The projection image construction unit 64 generates a partial image for one line of the projection image, for example, corresponding to one scanning position of the probe 11.

  For example, the projection image generation unit 60 corresponds to the scan position of the projection image based on the photoacoustic signal detected at each scan position before the scanning of the probe 11 is completed and the acquisition of the volume data is completed. Generate a partial image of the part. For example, in parallel with the scanning of the probe 11, the projection image generation unit 60 generates a projection image while acquiring volume data, and in accordance with the scanning of the probe 11, the projection up to the scanning position is imaged. The image may be displayed on the image display means 14 in real time.

  Next, the tomographic image generation unit 70 will be described. The tomographic image generation unit 70 includes a detection unit 71, a logarithmic conversion unit 72, a photoacoustic tomographic image construction unit 73, a detection unit 75, a logarithmic conversion unit 76, an ultrasonic tomographic image construction unit 77, and an ultrasonic / photoacoustic image synthesis unit. 74. Detection means 71 and 75 correspond to the detection means 232 shown in FIG. 1, and logarithmic conversion means 72 and 76 correspond to the logarithmic conversion means 233 shown in FIG. Further, the photoacoustic tomographic image construction means 73 and the ultrasonic tomographic image construction means 77 correspond to the image construction means 234 shown in FIG. The ultrasonic / photoacoustic image combining unit 74 combines the photoacoustic tomographic image and the ultrasonic tomographic image. At that time, it is preferable to synthesize both images so that the common portions of the subject in both images are superimposed and displayed.

  Instead of generating both the photoacoustic tomographic image and the ultrasonic tomographic image in the tomographic image generation unit 70, only one of them may be generated. In addition, an ultrasonic reconstructed image is input to the projection image generation unit 60, and in addition to the photoacoustic projection image, an ultrasonic projection image obtained by projecting the reflected acoustic signal in the depth direction at each of a plurality of scanning positions. It may be generated. Alternatively, the generation of the photoacoustic projection image may be omitted, and only the ultrasonic projection image may be generated.

  Returning to FIG. 4, the mode switching circuit 28 determines whether or not the user has instructed acquisition of photoacoustic volume data. The user can instruct the ultrasonic unit 12a to acquire volume data using an operation unit (not shown). When the user instructs acquisition of photoacoustic volume data, the mode switching circuit 28 sets the operation mode of the laser unit 13 to the second operation mode. For example, when the user instructs the generation of a photoacoustic tomographic image, the mode switching circuit 28 sets the operation mode of the laser unit 13 to the first operation mode.

  In the present embodiment, the mode switching circuit 28 sets the operation mode of the laser unit 13 to the second operation mode when acquiring photoacoustic volume data. By adopting the second operation mode, the timing is prioritized over the laser light amount, and the subject can be irradiated with light at a certain timing from the laser trigger. For example, by outputting the laser trigger signal at a predetermined cycle and moving the probe 11 at a constant speed using the probe scanning mechanism 15, photoacoustic signals can be acquired at constant intervals. On the other hand, except for the acquisition of photoacoustic volume data, by setting the operation mode of the laser unit 13 to the first mode, priority can be given to the amount of light emitted to the subject, and the detected photoacoustics. The signal-to-noise ratio (S / N ratio) of the signal can be improved.

  In the present embodiment, a photoacoustic projection image is generated by projecting a photoacoustic wave generation source in the depth direction. By generating the photoacoustic projection image in parallel with the scanning of the probe 11 and displaying the photoacoustic projection image on the display screen, the user can know the state inside the subject while performing the scanning. In this embodiment, the photoacoustic projection image is generated in parallel with the scanning of the probe 11 before the acquisition of the volume data is completed. As described above, when the photoacoustic projection image is generated while the probe 11 is being operated, it is faster than the case where the projection image is generated from the acquired volume data after the acquisition of the volume data is completed. A projection image can be generated and displayed.

  As mentioned above, although this invention was demonstrated based on the suitable embodiment, the photoacoustic image generation apparatus of this invention is not limited only to the said embodiment, Various correction and change are possible from the structure of the said embodiment. Those subjected to are also included in the scope of the present invention.

10: Photoacoustic image generation apparatus (photoacoustic image diagnostic apparatus)
11: Ultrasonic probe 12: Ultrasound unit 13: Laser unit 14: Image display means 15: Probe scanning mechanism 21: Reception circuit 22: AD conversion means 23: Image generation means 24: Trigger control circuit 25: Sampling control circuit 26: Control means 27: Transmission control circuit 28: Mode switching circuit 31: Trigger controller 32: Q switch laser 41: Reception memory 42: Data separation means 43: Photoacoustic image reconstruction means 44: Ultrasound image reconstruction means 45: Image synthesizing means 60: projected image generating section 61: absolute value converting means 62: depth direction data integrating means 63: logarithmic converting means 64: projected image constructing means 70: tomographic image generating sections 71, 75: detecting means 72, 76: logarithm Conversion means 73: Photoacoustic tomographic image construction means 74: Ultrasound / photoacoustic image composition means 77: Ultrasonic tomographic image construction means 80: Hole 1: holding plate 82: Ball screw 83: guide rod 84: Motor 231: image reconstruction means 232: detecting section 233: logarithmic converting means 234: image construction unit 321: a flash lamp 322: Q switch

Claims (16)

A trigger control circuit for outputting a trigger signal for instructing light emission;
The first operation mode and the second operation mode operate. In the first operation mode, light is emitted at an indefinite timing with respect to the trigger signal, and a synchronization signal indicating the light emission timing is output. A light source unit that emits light at a fixed timing with respect to the trigger signal in the operation mode,
A signal detection means for detecting a photoacoustic signal generated in the subject after the light emitted from the light source unit is irradiated on the subject;
Sampling means for sampling the detected photoacoustic signal;
A tomographic image generating means for generating a photoacoustic tomographic image based on the sampled photoacoustic signal;
When the light source unit operates in the first operation mode, the sampling of the photoacoustic signal in the sampling means is started in synchronization with the synchronization signal, and when the light source unit operates in the second operation mode, A photoacoustic image generation apparatus comprising: a sampling control circuit that starts sampling of the photoacoustic signal in the sampling means in synchronization with the trigger signal.   The light source unit includes a trigger controller and a Q-switched laser. When the trigger controller receives a trigger signal output from the trigger control circuit, excitation of the Q-switched laser is started, and excitation is performed in the first operation mode. 2. The Q switch is controlled at an indefinite timing after the start of the operation, and the Q switch is controlled at a constant timing from the start of excitation in the second operation mode. Photoacoustic image generation apparatus.   3. The photoacoustic image generation apparatus according to claim 2, wherein the trigger controller outputs a signal indicating a timing for controlling the Q switch in the first operation mode as a synchronization signal. 4.   The light source unit monitors the amount of emitted light at the time of light emission, and determines the timing of light emission based on the amount of light monitored at the time of previous light emission in the first operation mode. A photoacoustic image generation apparatus according to any one of claims 1 to 3.   5. The photoacoustic according to claim 1, further comprising mode switching means for switching an operation mode of the light source unit between the first operation mode and the second operation mode. Image generation device.   The mode switching unit sets the operation mode of the light source unit to the second operation mode when generating photoacoustic volume data indicating three-dimensional photoacoustic information. 5. The photoacoustic image generating apparatus according to 5.   7. The photoacoustic image generation according to claim 6, wherein in the generation of the photoacoustic volume data, the signal detection unit is scanned, and the sampling unit samples photoacoustic signals detected at a plurality of scanning positions. apparatus.   The light according to claim 7, further comprising a projection image generation unit configured to generate a photoacoustic projection image obtained by projecting the source of the photoacoustic signal in a depth direction at each of the plurality of scanning positions. Acoustic image generation device.   The projection image generating means generates a portion corresponding to the scanning position of the photoacoustic projection image based on the photoacoustic signal detected at each scanning position before the scanning is completed. The photoacoustic image generating apparatus according to claim 8, wherein the apparatus is a photoacoustic image generating apparatus.   The projection image generation means integrates the absolute value of the detected photoacoustic signal in the depth direction, and a portion corresponding to the scanning position of the photoacoustic projection image based on the integrated photoacoustic signal. The photoacoustic image generation device according to claim 9, wherein the photoacoustic image generation device is generated.   The photoacoustic image generation apparatus according to claim 9 or 10, wherein the projection image generation unit generates the photoacoustic projection image in parallel with scanning of the signal detection unit.   At each of the plurality of scanning positions, a reflected ultrasonic signal for the ultrasonic wave transmitted to the subject is detected, and in addition to the photoacoustic volume data, ultrasonic volume data indicating three-dimensional information of the reflected ultrasonic wave is generated. The photoacoustic image generation apparatus according to claim 7, wherein:   The projection image generation means generates an ultrasonic projection image obtained by projecting the reflected ultrasonic signal in the depth direction at each of the plurality of scanning positions instead of or in addition to the acoustic projection image. The photoacoustic image generating apparatus according to claim 12, wherein:   The photoacoustic image generating apparatus according to claim 7, further comprising a scanning mechanism that scans the signal detection unit in a predetermined scanning direction.   15. The photoacoustic image generating apparatus according to claim 14, wherein the scanning mechanism includes a holding unit that holds the signal detection unit, and a moving unit that moves the holding unit in a predetermined scanning direction. Outputting a trigger signal for instructing light emission to a light source unit operable in either the first operation mode or the second operation mode;
The light source unit emits light at an indefinite timing with respect to the trigger signal in the first operation mode and outputs a synchronization signal indicating light emission, and is constant with respect to the trigger signal in the second operation mode. Emitting light at timing;
A step of detecting a photoacoustic signal generated in the subject after the light emitted from the light source unit is irradiated on the subject;
When the light source unit operates in the first operation mode, the sampling of the photoacoustic signal is started in synchronization with the synchronization signal, and when the light source unit operates in the second operation mode, the trigger signal Starting the sampling of the photoacoustic signal in synchronization with,
Generating a photoacoustic tomographic image based on the sampled photoacoustic signal.

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